After months of contentious talks, one rejected contract offer and a strike threat, negotiators representing 850 state operating engineers reached another tentative labor agreement with Gov. Jerry Brown late Thursday.

The International Union of Operating Engineers Local 39 was the last state employee union without at least a tentative contract in place for the Legislature to consider before the curent session ends Aug. 31. Two unions representing state scientists and attorneys came to tentative terms with the administration last week. The remaining nine state-worker unions have contracts in place.

Members of the last three unions, which were all holding out for more pay, will have to approve the agreements for them to take effect.

Brown’s agreement with the operating engineers, who run heating, cooling, water and other complex systems for state facilities, is similar to the offer the rank-and-file rejected in June: a 2 percent raise retroactive to July 1 and a 2.5 percent increase on July 1, 2015. The contract expires a year later.

Unlike the first offer, however, the latest proposal gives employees a $250 bonus if they ratify it and allows employeess to cash out up to 40 hours of accrued leave.

The union’s leadership has long complained that their members’ salaries are well below those of counterparts in other government agencies and the private sector. Earlier this year after talks stalled, the union said it was considering various job actions, including a strike. A contract offered in June was rejected by members, who simultaneously authorized a strike and raised the specter of state buildings going without dependable air conditioning, water or power over the summer.

A call to the local seeking comment this morning wasn’t immediately returned.

Editor’s note, 1:18 p.m.: This post has been updated to include the tentative agreement’s leave cashout terms.